I'll start with the things I enjoyed (in no particular order):
-> gameplay was pretty solid and I know how easy it is to f*** up even tried and tested game formulas. The boost meter fills up pretty quick which is very satisfying.
-> you provided small descriptions for each and every death. I can always appreciate a little banter.
-> you integrated highscores and all that, which adds tons of replayability.

Now, the things that I didn't enjoy that much (I'll number them so I can provide my opinion below on how you could improve those aspects):
1. each sprite is pretty basic and wholesome on its own, but the platforms are pretty boring to look at and don't seem to be from the same project or asset pack or something (I know you probably made the sprites yourself, but the main character and the enemies seem to be 8 bit and highly detailed and the platforms seem to be 16 bit - which feels weird).
2. the background is very boring.
3. sometimes you get killed because the perspective is zoomed in too much and you don't get enough time to react.
4. no music.

Suggestions:
1. make a new set of platforms that don't feel so flat and randomly generate them like before (randomize their hue or brightness a little bit too - so you could make like 5 platforms and they would feel like 100).
2. draw a few distant planets or something like that and randomize the color of the stars. You could also generate the actual background color with an RGB function that takes a random red value (between 100-150 or something).
3. you could instantiate the enemies sooner and generate an arrow or something that follows their x position so that you could know what awaits you.
4. add music :)